Four peptides, salmon calcitonin (sCT), the 8-22 amino acid portion of sCT (CT15), an LHRH superagonist, triptorelin (DP) and a somatostatin analogue (RC160) were studied for adsorption to poly(D,L-lactide-co-glycolide) (PLGA) as a function of peptide and polymer concentration. The adsorption of sCT and DP to the polymer showed a primary transient-equilibrium followed by a more rapid and extensive adsorption without reaching a concentration plateau for sCT which occurred earlier with higher peptide concentration. The amount of adsorption for CT15 was much lower than that for sCT and DP and RC160 showed no adsorption. Adsorption isotherms of sCT and DP were fitted to a Langmuir-type of relationship and the monolayer concentration was close to that observed in the kinetic studies or that calculated by the theoretical approach.
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